This invention relates to a spraying gun for atomizing, i.e. pulverizing or spraying substances in the liquid state, provided with a closure head for cartridges, as well as a gun head including a pulverizer, a regulating valve and members for operating the valve. With the spraying gun according to the invention, paints, lacquers, spray solutions and other materials can be atomized and sprayed onto various objects.
Social and economic developments cause people to increasingly do their own repairing of their personal possessions and living quarters as they require repairs, and/or to maintain them themselves. Such repair and maintenance jobs include for example the painting of apartments, week-end homes and doors or windows, anti-corrosion protection of metal objects, painting and polishing of furniture, repairing damaged sprayed enamels of vehicles, plant and tree spraying, etc.
The performance of such jobs is hampered since the hobbyist or do-it-yourselfer does not have at hand a spraying gun which is useful for all purposes, is cheap and operates safely and simply.
The earliest devices in the particular field of this invention were the pneumatic spraying guns. In these, the liquid to be atomized is forced through the atomizer together with an atomizing medium in the gas state, preferably, air. The disadvantage of pneumatic spraying guns resides in that, on the one hand, a high-pressure atomizing medium has to be used and major portion of the applied pressure energy is not exploited. On the other hand, the atomizing medium entrains and scatters a substantial portion of the atomized substance when impinging upon the surface being coated. As a result, these known devices are rather energy-demanding, on the one hand, and on the other, they operate with large material losses, Pneumatic spraying guns cannot be considered for hobbyists' or do-it-yourself projects.
To eliminate the above disadvantages, the so-called airless spraying has been developed in which the liquid to be atomized and sprayed is forced through the atomizer by itself. The liquid to be atomized is brought to the atomizer by the aid of pressure produced within the gas space of the supply container, or by means of a pump.
Industrial devices usually pulverize or atomize at a pressure of 70-250 att (atmospheric over-pressure, i.e. pressure in excess of atmospheric pressure) with performances of 2000-4500 cm.sup.3 /minute by the aid of screw- or gear-type pumps. The supply container is designed as a large-size, stationary apparatus. The atomizers of the spraying guns are usually so-called planar pulverizers, plan-spray and/or flat-nozzle systens. It follows clearly from the above that these are not suitable for the hobbyist or do-it-yourselfer.
The devices that could be considered for do-it-yourself or hobbyists' purposes work at 30-35 att with performances of 100-130 cm.sup.3 /min. The Mistral-type devices which are most widely used, bring the liquid to be atomized to the atomizer by a piston that freely swings in an electromagnetic field that is built into a so-called rising conduit. The atomizer is generally of a spinning-chamber design. The supply container is in turn mounted onto the spraying gun and the rising conduit is immersed into the liquid to be atomized.
The major disadvantages of the devices that have the supply containers mounted on the spraying guns are that the possible operational positions of the spraying guns depend on the containers. Namely, if the liquid to be atomized does not cover the mouth opening of the rising conduit as result of a change in position of the spraying guns, understandably the guns can not atomize. This situation arises during operation when spraying onto surfaces that are above head.
A further drawback of the known devices is that the spraying guns have a very complicated construction which increases their acquisition or purchase costs, while the amount of work needed for cleaning them subsequent to use is substantially increased. For the most part the rinsing with a solvent is not sufficient. The necessary degree of cleaning is possible only by completely disassembling the gun and by individually washing the component parts. In addition, the inner mechanisms of the known spraying guns are very sensitive during operation to the fineness of the substance to be atomized and often become clogged.
The Mistral-type spraying guns are particularly disadvantageous when the MOHS hardness of the paints that constitute the major part of the substances to be atomized is between the values of 9-9.5 so that the piston is ruined after a relatively short time.
It is finally a common drawback of all known spraying guns that they cannot be operated without a power source, such as an electric power line or a separate power unit.
The reliance of spraying guns on a power source was eliminated by the apparatus made according to the Hungarian Pat. No. 155,739 wherein the pressure energy of a compressed gas cartridge is used for liquid atomization. With this device, the gas pressure of the cartridge increases the inner pressure of the gas space within the supply container, and the liquid is forced through the atomizer by means of this excess pressure.
However, this device is also disadvantageous because of its dependence on the position of the supply container and its complicated construction. As a further drawback one can mention that the atomizing medium which contacts the liquid to be sprayed in the supply container is dissolved in the liquid as a function of the excess pressure, and the bubbles exiting to the atmosphere manifest a phenomenon as if the spraying gun is being operated with pneumatic atomizing and spraying.